The field of the present invention is related to biomarkers of health, and more specifically to one or more of detecting, diagnosing, screening, tracking over time, or ruling out, one or more conditions such as high blood pressure and the harmful cardiovascular effects of high blood pressure. Examples of harmful effects of high blood pressure can include one or more of inflammation, coronary artery disease, stable plaques, unstable plaques, or other vascular factors related to the onset of heart disease and heart attack in humans.
Prior methods and apparatus of measuring biomarkers are less than ideal in at least some respects. Prior methods and apparatus of measuring blood pressure and diagnosing subjects can be less than ideal in at least some instances. Although blood pressure measurements can be used to assess the health of a subject and guide treatment, the prior methods and apparatus can be less than ideal. Blood pressure measurements based on the sphygmomanometer, also referred to as a blood pressure cuff, can have problems and deficiencies in at least some instances. For example, blood pressure cuff measurements can result in less than ideal measurements that may be related to one or more of the following: observer error; systematic intraobserver and interobserver errors; terminal digit preference, rounding to favorite digit; observer prejudice; white coat hypertension (high only in doctor's office); masked hypertension (normal in office, high at other times of day); instrument error; defective control valve; improper fit of cuff, too large or too small; inadequate length of tubing; connections not airtight; position of manometer causes reading error; placement of cuff error; diastolic dilemma (muffling of sounds can occur 10 mm before complete disappearance); two arms exhibiting different readings; deflation too rapid. These errors can lead to inaccurate blood pressure readings that may be related to improper diagnoses in at least some instances. For example, errors as large as 20 mm Hg may occur in at least some instances.
If a subject is incorrectly diagnosed as having high blood pressure when actually having low blood pressure, this person may be placed on a daily blood pressure medication. Many of these medications may have side effects, and more people than would be ideal can be subjected to the side effects of blood pressure medications. Also, blood pressure measurement errors may result in a person who actually has high blood pressure being misdiagnosed as having low blood pressure. An incorrect diagnosis for a subject with high blood pressure can result in that subject not receiving appropriate medication, such that the high blood pressure may not be untreated in at least some instances. Inappropriate management of high blood pressure can result in injury to the subject and may even be fatal in at least some instances, and it would be helpful to have fewer misdiagnoses of high blood pressure.
Work in relation to embodiments suggest that it would desirable to have a record of blood pressure and of cardiovascular health over a period of time, rather than an instantaneous measurement like brachial cuff pressure.
Although blood chemistry is the gold standard for screening, diagnosis, and therapy in health wellness and medicine, the prior methods are less than ideal in at least some respects. Currently, a blood panel is requested by a physician and the patient is instructed to travel to a blood laboratory where a phlebotomist can draw blood from the antecubital vein into a series of special collection tubes. The blood is then sent to a central blood chemistry laboratory where it is chemically analyzed using numerous wet chemical assays that have been developed and validated over the years. More recently, a small portion of these tests can be performed in a physician's office using specialized machines employing enzymatic assays. Such delivery of blood to various locations can be less than ideal.
Blood chemistry testing is rapidly moving to the point-of-care (POC) for many reasons. The biggest of these are cost and compliance. Blood testing in the POC and eventually in the home can significantly decrease healthcare costs, can be trackable and reportable, and can be immediate and actionable, sticky, and socially supportive compared to central lab testing. However, current central lab methods often do not translate to the POC and the home, since they often require complicated wet chemistry and expensive instrumentation.
In light of the above, it would be desirable to provide improved methods and apparatus for measuring biomarkers of a patient, such as biomarkers useful in determining blood pressure. Ideally such methods and apparatus would provide a more accurate reading of blood pressure with less variability and fewer false negatives and false positives for high blood pressure, provide a more accurate determination of central blood pressure, allow improved treatment and management of blood pressure, and provide an indicator of blood pressure and cardiovascular health over time.